It is known to use separate air/fuel feedback control systems for each cylinder bank of a V-type engine. Each air/fuel feedback system adjusts fuel delivered to one cylinder bank in response to a feedback variable derived from an exhaust gas oxygen sensor coupled to that particular cylinder bank. Such a control system results in the air/fuel ratio of each bank oscillating about an average air/fuel ratio which is typically stoichiometry.
Japanese Patent Publication SHO-60-190631 describes a modification of such air/fuel feedback system wherein the air/fuel feedback system of one cylinder bank is slaved to the air/fuel feedback system of the other cylinder bank. Allegedly, the air/fuel oscillations of each bank are thereby forced out of phase to minimize torque fluctuations between the banks.
The inventors herein have recognized and solved numerous problems with the above approaches. One problem is that by slaving the second air/fuel feedback system to the first air/fuel feedback system, the time response and sensitivity of the second air/fuel feedback system are not optimal.